/*
 * Copyright (c) 2010 The Boeing Company
 * Copyright (c) 2014 Michele Segata <segata@ccs-labs.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Gary Pei <guangyu.pei@boeing.com>
 */

#include "NistErrorRate.h"
#include <omnetpp.h>

namespace Veins {

NistErrorRate::NistErrorRate ()
{
}

double NistErrorRate::getBpskBer (double snr)
{
    double z = std::sqrt (snr);
    double ber = 0.5 * erfc (z);
    return ber;
}


double NistErrorRate::getQpskBer (double snr)
{
    double z = std::sqrt (snr / 2.0);
    double ber = 0.5 * erfc (z);
    return ber;
}


double NistErrorRate::get16QamBer (double snr)
{
    double z = std::sqrt (snr / (5.0 * 2.0));
    double ber = 0.75 * 0.5 * erfc (z);
    return ber;
}


double NistErrorRate::get64QamBer (double snr)
{
    double z = std::sqrt (snr / (21.0 * 2.0));
    double ber = 7.0 / 12.0 * 0.5 * erfc (z);
    return ber;
}


double NistErrorRate::getFecBpskBer (double snr, uint32_t nbits, uint32_t bValue)
{
    double ber = getBpskBer (snr);
    if (ber == 0.0)
        return 1.0;

    double pe = calculatePe (ber, bValue);
    pe = std::min (pe, 1.0);
    double pms = std::pow (1 - pe, (double)nbits);
    return pms;
}


double NistErrorRate::getFecQpskBer (double snr, uint32_t nbits, uint32_t bValue)
{
    double ber = getQpskBer (snr);
    if (ber == 0.0)
        return 1.0;

    double pe = calculatePe (ber, bValue);
    pe = std::min (pe, 1.0);
    double pms = std::pow (1 - pe, (double)nbits);
    return pms;
}


double NistErrorRate::calculatePe (double p, uint32_t bValue)
{
    double D = std::sqrt (4.0 * p * (1.0 - p));
    double pe = 1.0;
    if (bValue == 1)
    {
        // code rate 1/2, use table 3.1.1
        pe = 0.5 * ( 36.0 * std::pow (D, 10)
        + 211.0 * std::pow (D, 12)
        + 1404.0 * std::pow (D, 14)
        + 11633.0 * std::pow (D, 16)
        + 77433.0 * std::pow (D, 18)
        + 502690.0 * std::pow (D, 20)
        + 3322763.0 * std::pow (D, 22)
        + 21292910.0 * std::pow (D, 24)
        + 134365911.0 * std::pow (D, 26)
        );
    }
    else if (bValue == 2)
    {
        // code rate 2/3, use table 3.1.2
        pe = 1.0 / (2.0 * bValue) *
                ( 3.0 * std::pow (D, 6)
        + 70.0 * std::pow (D, 7)
        + 285.0 * std::pow (D, 8)
        + 1276.0 * std::pow (D, 9)
        + 6160.0 * std::pow (D, 10)
        + 27128.0 * std::pow (D, 11)
        + 117019.0 * std::pow (D, 12)
        + 498860.0 * std::pow (D, 13)
        + 2103891.0 * std::pow (D, 14)
        + 8784123.0 * std::pow (D, 15)
                );
    }
    else if (bValue == 3)
    {
        // code rate 3/4, use table 3.1.2
        pe = 1.0 / (2.0 * bValue) *
                ( 42.0 * std::pow (D, 5)
        + 201.0 * std::pow (D, 6)
        + 1492.0 * std::pow (D, 7)
        + 10469.0 * std::pow (D, 8)
        + 62935.0 * std::pow (D, 9)
        + 379644.0 * std::pow (D, 10)
        + 2253373.0 * std::pow (D, 11)
        + 13073811.0 * std::pow (D, 12)
        + 75152755.0 * std::pow (D, 13)
        + 428005675.0 * std::pow (D, 14)
                );
    }
    else
    {
        ASSERT (false);
    }
    return pe;
}


double NistErrorRate::getFec16QamBer (double snr, uint32_t nbits, uint32_t bValue)
{
    double ber = get16QamBer (snr);
    if (ber == 0.0)
        return 1.0;

    double pe = calculatePe (ber, bValue);
    pe = std::min (pe, 1.0);
    double pms = std::pow (1 - pe, static_cast<double> (nbits));
    return pms;
}


double NistErrorRate::getFec64QamBer (double snr, uint32_t nbits, uint32_t bValue)
{
    double ber = get64QamBer (snr);
    if (ber == 0.0)
        return 1.0;

    double pe = calculatePe (ber, bValue);
    pe = std::min (pe, 1.0);
    double pms = std::pow (1 - pe, static_cast<double> (nbits));
    return pms;
}


double NistErrorRate::getChunkSuccessRate (unsigned int datarate, enum Bandwidth bw, double snr_mW, uint32_t nbits)
{
    //get mcs from datarate and bw
    enum PHY_MCS mcs = getMCS(datarate, bw);

    //compute success rate depending on mcs
    switch (mcs)
    {
    case MCS_OFDM_BPSK_R_1_2:
        return getFecBpskBer(snr_mW, nbits, 1);
        break;
    case MCS_OFDM_BPSK_R_3_4:
        return getFecBpskBer(snr_mW, nbits, 3);
        break;
    case MCS_OFDM_QPSK_R_1_2:
        return getFecQpskBer(snr_mW, nbits, 1);
        break;
    case MCS_OFDM_QPSK_R_3_4:
        return getFecQpskBer(snr_mW, nbits, 3);
        break;
    case MCS_OFDM_QAM16_R_1_2:
        return getFec16QamBer(snr_mW, nbits, 1);
        break;
    case MCS_OFDM_QAM16_R_3_4:
        return getFec16QamBer(snr_mW, nbits, 3);
        break;
    case MCS_OFDM_QAM64_R_2_3:
        return getFec64QamBer(snr_mW, nbits, 2);
        break;
    case MCS_OFDM_QAM64_R_3_4:
        return getFec64QamBer(snr_mW, nbits, 3);
        break;
    default:
        ASSERT2(false, "Invalid MCS chosen");
        break;
    }

    return 0;
}

}
